The present invention relates to vehicles in general, and more particularly to improvements in rail-mounted conveyances, especially to improvements in conveyances which can be used in mines and other types of underground excavations to transport ore from and/or to transport workers and/or material into the excavation. Still more particularly, the invention relates to improvements in rail-mounted conveyances of the type wherein the superstructure (e.g., a receptacle for deposition of ore therein or thereon) is mounted on several undercarriages one of which permits the superstructure to move about three mutually inclined axes with respect to the one undercarriage and/or vice versa.
Three-dimensional articulation of the superstructure with reference to one of the undercarriages is necessary when the conveyance travels along an arcuate path which slopes upwardly or downwardly. If the conveyance is to take a curve which is disposed in a horizontal plane, each undercarriage should be free to turn with reference to the superstructure about a vertical axis, i.e., about an axis which is normal to the plane of the curve. If a straight path slopes upwardly or downwardly, the undercarriages should be free to turn with reference to the superstructure and/or vice versa about horizontal axes which extend transversely of the direction of travel of the conveyance. Finally, and as mentioned above, if the rail or rails slope upwardly in a curve, one of the undercarriages must be free to pivot about a third axis, namely, about an axis which extends substantially in the direction of travel of the conveyance and is normal to the other two axes. This is due to the fact that mere movability of the two carriages about a vertical and about a transverse horizontal axis would not enable one of the undercarriages to perform with reference to the other undercarriage that movement which is necessary to keep the wheels of both carriages in contact with the rails while the two undercarriages travel along an arcuate path and one of the undercarriages is located at a level above the other undercarriage. The situation is further complicated due to the fact that, in a curve, one of the rails is normally located at a level above the other rail. Absence of exact parallelism of the rails and/or the placing of one of the rails at a level above the other rail is accounted for within an undercarriage in that the wheels at one side of the conveyance are mounted on a first rocker arm, that the wheels of the same undercarriage at the other side of the conveyance are mounted on a second rocker arm, and that the two rocker arms can turn about the horizontal axis which extends transversely of the direction of movement of the conveyance.
The ability of the superstructure in a conventional conveyance to turn about an axis (hereinafter called X-axis) which extends in the direction of travel of the conveyance necessitates the placing of the center of gravity of the load to a higher level because the platform which carries the load must be raised sufficiently to avoid interference with the one or the other rocker arm when the platform is pivoted about the X-axis. This affects the stability of the conveyance and of the load thereon. The just discussed drawback of heretofore known conveyances which employ an undercarriage capable of turning about three axes including the X-axis cannot be overcome by widening the track (i.e., the distance between the two rails). Moreover, a widening of the track is often extremely difficult or plain impossible. This is due to the fact that, if the distance between the rails (and hence the distance between the two rocker arms of the three-dimensionally movable undercarriage) is increased, the distance between the level of the rocker arms and the platform must also be increased if the extent of pivotability of the platform about the X-axis is to remain unchanged.